In the photographic field, two-equivalent-type couplers are now in general use in respect that they enable to obtain maximum dye densities and photographic sensitivities with a small amount of silver. In the case of two-equivalent-type yellow couplers, there are known, as the active site substituent thereto, for example, those aryloxy groups as disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 87650/1974 and U.S. Pat. No. 3,408,194; those oxazolyloxy groups as disclosed in Japanese Patent O.P.I. Publication No. 131325/1976, those chroman-4-oxy groups as disclosed in Japanese Patent O.P.I. Publication No. 139333/-1976; those tetrazolyloxy groups as disclosed in Japanese Patent O.P.I. Publication No. 43426/1977; those 5-pyrazolyloxy groups as disclosed in Japanese Patent O.P.I. Publication No. 150631/1977; those nitrogen-containing heterocyclic groups as disclosed in Japanese Patent O.P.I. Publication No. 115219/-1977; those urazole groups and hydantoin groups as disclosed in Japanese Patent Examined Publication No. 33410/1976; and those arylthio groups as disclosed in U.S. Pat. No. 3,227,554.
On the other hand, with the progress of silver halide light-sensitive photographic materials, the demand for improving the characteristics of couplers is becoming increasingly severe, and the above-mentioned two-equivalent-type yellow couplers are also demanded to be improved on the color developing efficiency. Therefore, various attempts have hitherto been made in designing coupler molecules; for example, there has been a proposal to improve the color formability by introducing an alkoxycarbonyl group or an N-substituted or unsubstituted alkylsulfonamido group or an arylsulfonamido group to the ballasting constituent. Such attempts, however, cannot be considered to have contributed adequately to the improvement.
Such yellow couplers have the disadvantage that the color formability thereof varies largely according to the pH of a color developer solution. The pH of the color developer solution generally varies to some extent according to the color developing agent, couplers, etc., contained therein, and particularly where a large quantity of color light-sensitive materials are processed running in an automatic processor, it is very difficult to have the pH maintained optimum due to the silver halide ions dissolved out of the light-sensitive material into the solution, accumulation of various additives in the solution, oxidation of the solution by the air, and the like. Accordingly, the development of an yellow coupler which is excellent in the color formability, wherein the color formability is hardly affected by the pH of a color developer solution, is urgently needed.
Further, in recent years, the demand for true color reproduction from the side of users who desire to have the real color of a subject vividly reproduced as it is in their own photographs has been increasing. As a concrete means to meet such a demand, reducing or dissolving the color turbidity of a formed dye as well as making the color tone of the dye clear may be feasible by developing such a coupler that the dye formed in the coupling reaction thereof with the oxidized product of a color developing agent has a sharp-cut wave-form-having visible absorption spectrum However, any research and development of such couplers from this point of view cannot be deemed to have been adequately made to date.